The oil temperature is regulated by the cooling system. Doesn't matter if oil is new or old it will level out at the same temp.

FYI- Bear in mind, that over a 20,000 mile oil change interval there will be oil added that will improve the effectiveness of the oil and we don't know the conditions surrounding the oil change interval.

Most of the time there is no way to know if an oil change interval caused an engine problem but it is a fact that the more miles on the oil the less effective it becomes, thus the more miles between changes the more risk. Small risk or big risk, I don't consider the extent of the risk.

If I use $100 as the cost of an oil and filter change, and I drive 10,000 miles a year and I change the oil every 5000 miles I spend $200 a year. If I have a seemingly oil related engine problem and it only costs $1,000. it would take 5+ years of oil and filter changes before I would have a negative payback.

I would expect a negative payback if I started from 0 miles on the clock. But, most of us now have 75,000++ miles on our vehicles. The moving parts in the engine are metal to metal, with oil being the only reason they don't eat each other.

We certainly should agree that oil degrades as miles accumulate on the engine. Think of it this way. How many ounces of typical oil contaminates would you pour into your engine, regardless of the oil filter you use, and put another 10,000 miles on that oil?

You can claim it is ridiculous if you like. I base my personal assessment on having grown up in a family owned independent automotive shop back in the 70's, having earned a mechanical engineering degree, and then spending a few decades in a (non BMW) dealership heavy equipment business, with responsibility for managing long term maintenance contacts, scheduled oil sampling labs, national warranty programs, shop and field service delivery, and so on.

With respect to BMWs, the current one is our 6th, not counting a motorcycle. I track oil consumption, and all repairs, and have records for every vehicle back to 1976. I manage service costs for the lowest total lifetime cost of ownership. I do my own work when I can, use a family owned shop when it is handy to have a hoist, and use the dealer for most routine servicing because it is convenient.

You reference sludge, but don't qualify if you mean oil sludge, ie dark brown, with byproducts of combustion, or condensate paste (not really sludge, occurs due to not getting the oil warm enough to burn off the moisture, and often mistakenly called sludge here and elsewhere).

I don't agree that BMWs have a bad reputation for reliability. They have a reputation for not being particularly tolerant of neglect and abuse, whether in operation or maintenance. Vehicles with low reliability often experienced that neglect. Buying older vehicles with unknown operation and service history, that may be all that some have experienced.

I agree that regular servicing is important. Being conservative, I do my services before they are due. When I change the oil at 20,000 km on a vehicle designed for a 28,000 km OCI that is early, not extended. Running it to 40,000 would be extended. Posters regularly refer to following the manufacturer's recommendations as extended, when they would have to go back to the nineties to find a maintenance schedule for shorter intervals. 10,000 mile intervals came out in 1992, and 15,000 miles intervals cameout in 1999. That is a lot of years of experience. Neither vehicles, nor oils, are the same as in past decades, when we routinely changed oil at 3000 miles.

With respect, I think I do know what the condition of my vehicle is.

Jeff

I don't think many are running 20,000 miles. I typically run 20,000 km. But in that 20,000 km, I don't add any oil. I could just about get a litre in it by the end, but I change it instead.

I think we had this discussion previously ;)

The additives in the oil degrade, in terms of stabilizers, TBN, etc. Agree. That matters once they are used up, or reach a critical level. Until then, not so much.

However, the oil does a better job of lubricating once broken in, with lubricity improving up to something like 12,000 miles IIRC, in the study I posted previously.

Another way of phrasing the ability of the oil to hold those contaminants in suspension, is to consider the impact of sump capacity. Many with 3000 mile OCI habits are used to 4-5 quart sumps. Double the sump size, double the capacity for managing those contaminants, before requiring a drain and fill.

Jeff

Well said and I totally agree :thumbup:

You maybe right in many areas. One problem I see is the word typical is so wide you can drive a train through it. IMHO Oil development, metallurgy, constant engine temps, and engine tolerances in the last 15-20 years have improved so much that any comparison on "what used to be true" and "How often should I change my oil" is based on what has been said over and over again - What is your preference and what does repeated oil analysis show trending?

Bottom Line: Change your oil based on your location, temps and driving cycles (more frequently than the oil change dash lights recommend!), change the filter every time with a quality one, Keep the oil level near the full line and 99% of the issues mentioned will not occur. Everyone agree? :stickpoke

Let's not start another Oil Thread. We will run out of readers in approx 10 postings.

Next issue: What air pressure do you use (Cold only) with what tire size? :thumbup:

I'm not going to get into another debate with you but I will try to, only once, clarify my point.

Yes, I know it assumes there will be a $1,000 problem that is seemingly oil related within 5 years and a 5,000 mile oil change interval will prevent that seemingly oil related engine issue from happening I also used very conservative numbers in my example which included total cost of the oil not the difference.

The determining factor to this is whether or not one believes oil at peak performance capabilities matters and, if so, how much.

If I understand you correctly, you believe there is little or no risk changing oil at a 10,000 mile interval. I am not challenging any oil change interval I just don't see the need to take any risk.

I am merely attempting to explain my point of view. I am not saying anyone is making a mistake by choosing a longer oil and filter change interval.

Using my assumptions and your calculation (paybacks generally have assumptions in them) if I don't have an oil related problem in ten years that I would have had if I used a longer oil change interval, I am money ahead, a positive payback.

36psi cold... on 20's.

As for the oil. Changing it more frequently is just additional piece of mind, which can be worth more than any savings (or cost) in terms of prevented damage. Change your oil at the interval that makes you feel comfortable, but before the SI lights indicate it's due.

:iagree: